The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine produces power by burning fuel. A portion of the power produced by the engine is used to propel a vehicle and the other portion of the power is consumed as thermal energy. In particular, coolant absorbs thermal energy during circulating through the engine and radiates absorbed heat through a radiator.
If coolant temperature is low, frictional force increases due to increased viscosity of an engine oil, fuel consumption increases, a temperature of an exhaust gas rises slowly to increase time for activating a catalyst, and quality of the exhaust gas is deteriorated. Further, time for activating a heater also increases.
If the coolant temperature is excessively high, knocking occurs. To suppress occurrence of knocking, ignition timing should be controlled. In this case, engine performance may be deteriorated. In addition, if a temperature of a lubricant is excessively high, lubrication may be deteriorated.
Therefore, the coolant temperature at a specific position of the engine maintains high while the coolant temperature at another position of the engine maintains low. Recently, it has been developed and applied that supply of coolant to several cooling components is controlled by one coolant control valve unit.
Meanwhile, in order to control coolant supplied to a radiator, a heater, an oil cooler, and so on by using one coolant control valve unit, several valves are disposed in a housing and a cam is configured to selectively lift such valves. In this case, the cam rotates and controls opening or closing of the valves.
In this configuration, however, we have discovered that frictional abrasion occurs between the cam and the valves and a gap can be formed between the cam and the valves. In this case, it may be hard to precisely control opening timing or closing timing of the valves, or durability of components may be deteriorated. Therefore, management and maintenance costs may increase.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.